Development of the concepts of volume filling of micropores in the adsorption of gases and vapors by microporous adsorbents

Zhang

et al. 2016

Environ. Sci. Technol.

114

3-D MnO 2 ion cages (CMO) were fabricated and shown to have a high capacity for lithium removal from wastewater. CMO had a maximum Li(I) adsorption capacity of 56.87 mg/g, which is 1.38 times greater than the highest reported value (41.36 mg/g). X-ray photoelectron spectroscopy indicated that the stability of the −Mn−O−Mn−O− skeleton played an essential role in Li adsorption. The lattice clearance had a high charge density, forming a strong electrostatic field. The DubininAshtakhov (DA) site energy distribution model based on Polanyi theory described the linear increase of Li adsorption capacity (Q 0 ) with increasing temperature (Q 0 = k 3 × E m + d 3 = k 3 × (a × T) + d 3 ). Furthermore, the pore diffusion model (PDM) accurately predicted the lithium breakthrough (R 2 ≈ 0.99). The maximum number of bed volumes (BVs) treated was 1374, 1972, and 2493 for 200 μg/L at 20, 30, and 40°C, respectively. Higher temperatures increased the number of BVs that may be treated, which implies that CMO will be useful in treating industrial Li(I) wastewater in regions with different climates (e.g., Northern or Southern China).

Section: Environmental Science and Technologymentioning

confidence: 99%

Capturing Lithium from Wastewater Using a Fixed Bed Packed with 3-D MnO₂ Ion Cages

Zhang

et al. 2016

Environ. Sci. Technol.

114

“…Several models were used to investigate the effect of the catalyst on the textural properties of carbon aerogels. Among these models were used Brunauer-EmmettTeller (BET) [38][39][40][41][42][43], Dubinin-Astakhov (DA) [32,44], the Barret, Joyner and Halenda (BJH) [31] and density functional theory (DFT) [33][34][35][36][37].…”

Section: Porous Characterization Of R/f Carbon Aerogelsmentioning

confidence: 99%

“…The volume of the primary micropores (< 0.7 nm) was determined by the application of Dubinin-Astakhov (DA) equation [25,32,44] that corresponds to the volume adsorbed to the (P/P°) = 0.1 as well as the distribution of pore size. The mesopores volume (Vmes) was calculated as the difference between the volume of nitrogen adsorbed to the (P/P°)= 0.95 and (P/P°) = 0.10.…”

Section: Porous Characterization Of R/f Carbon Aerogelsmentioning

confidence: 99%

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Carbon Aerogels: a study with different models of the effect resorcinol/catalyst at different ratios after pyrolysis and the effect on textural properties

et al. 2017

Eight samples of carbon aerogels were prepared at various resorcinol/catalytic (R/C) ratios (ranging from 25 to 1500) and followed the changes in structure after pyrolysis. Isotherms of N2 to 77 K were determined to calculate the textural parameters using Dubinin-Astakhov (DA), Barret Joyner and Halenda (BJH), Non-Local Density Functional Theory (NLDFT) and Quenched Solid Density Functional Theory (QSDFT) models. The results generated two series of samples. In series I, a single type of pores developed (microporous, at low R/C weight ratio). Series II developed mesoporosity to top gears of R/C (> 400). The specific areas ranged from 64 to 990 m 2 /g. Additional models were applied to the materials synthesized, which allowed for adjustment to a system of "cylinder-slit" pores by applying the QSDFT kernel, with an error percentage ranging from 0.03 to 0.74.

“…Frequently, and for various reasons, deviations from linearity are observed in such plots; these have been discussed in detail elsewhere (Marsh and Rand 1970) but usually the main linear region, which encompasses most of the micropore filling region of the adsorption isotherm, is sufficient to allow a confident extrapolation to the y-axis to obtain W 0 ; this method gives a straightforward and sound basis for comparing the micropore capacities of different carbons. Replacing the square term in (1) with an exponential (n) which describes the micropore size distribution leads to the more general Dubinin-Astakhov equation (Dubinin and Astakhov 1971). The difference between W 0 from (1) and the total adsorbed volume (V T ) at p/p s near to saturation (0.95-0.98 in practical terms) allows a first-order approximation of the wider (>2 nm) pores.…”

Section: Theorymentioning

confidence: 99%

Effects of active carbon pore size distributions on adsorption of toxic organic compounds

Branton

Bradley²

2010

Adsorption

The use of active carbons for the removal of toxic organic compounds, for example from air or smoke, is of significant interest. In this paper, the equilibrium and dynamic adsorption characteristics of two active carbons are explored; one microporous coconut based and the other micro-mesoporous derived from a synthetic resin. Benzene, acetaldehyde and acrylonitrile were chosen as the probe toxicant vapours and adsorption was measured at a temperature of 298 K. The nitrogen equilibrium data (at 77 K), analysed using the BET, Dubinin-Radushkevich equations and DFT models, showed a higher overall adsorption capacity, more supermicroporosity and a higher proportion of pores wider than 2 nm for the synthetic resin based material. A micropore distribution biased toward the ultramicropore widthrange was observed for the nutshell material. As a consequence, the characteristic adsorption energies in micropores are higher for the nutshell material than the resin based carbon. The effect of these different pore size characteristics on the adsorption kinetics, obtained by fitting the data to the linear driving force (LDF) model, is that the resulting adsorption rate constants are higher across much of the relative pressure range (p/p s ) studied for the resin based carbon compared to the nutshell material. Significantly, the wider pores of the resin-based carbon result in higher rates of adsorption in the micropore filling domain. When evaluated P. Branton ( ) Group Research and Development, British American Tobacco, Regents Park Road, Millbrook, Southampton SO15 8TL, UK e-mail: peter_branton@bat.com R.H. Bradley Carbon Technology, MatSIRC Ltd., Penrith, Cumbria CA10 1NW, UK e-mail: matsirc@btinternet.com under dynamic conditions in cigarette smoke, improved toxicant removal was observed using the resin based carbon.